2019 Mac Pro CPU upgrade?

In Apple's opinion, anything that requires heatsink compound is not user-upgradable.

It is really early in the product cycle to be asking about this. The first regular deliveries may not have even arrived. But in general, with a new product, you need to buy what you will need for the first year from stock, as there is no aftermarket at this writing.

Of course it is upgradable. I am amazed that Grant said it is not because it has compound. Adding compound to a CPU is extremely easy. When I taught 7th grade STEM, I taught my students how to do it.